This invention relates to an underwater dive vehicle of the type which may be used for propelling divers to underwater locations, and more particularly to a powered underwater vehicle in which the buoyancy may be reduced as the vehicle descends to greater depths in the water and remains neutrally buoyant at depth.
This is an improvement over the dive vehicle described and claimed in my U.S. Pat. No. 6,065,419 dated May 23, 2000 and entitled Underwater Dive Vehicle. In that patent there is disclosed and claimed a dive vehicle which employs a flexible and resilient gas filled buoyancy element which may be in the form of a resilient bladder or a closed cell resilient sponge material. The present invention incorporates a plurality of rigid, foamed substantially incompressible second buoyancy elements which may be selectively attached to or removed from the vehicle to adjust buoyancy and thereby achieve neutral buoyancy according to the weight of the vehicle and its loan and/or according to the buoyancy of the waters surrounding the vehicle.
Small powered underwater dive vehicles for taking one or two divers to underwater locations usually comprise a motor having a drive shaft which is operably connected to a propeller, a battery for energizing the motor and a control switch for selectively energizing the motor. Such devices are illustrated and described, for example, in U.S. Pat. No. 5,379,714, No. 4,864,959 and No. 4,996,938. Such vehicles, however, have encountered problems of buoyancy and leakage. Leakage is a particular problem when the vehicle is taken to substantial depths where the pressure may be several atmospheres. For every 10 meters of descent in sea water, an additional atmosphere of pressure is placed on the vehicle and its parts. Thus, at a depth of 30 meters or approximately 100 feet, there are 3 atmospheres of pressure, and the pressure corresponding increases as greater depths are attained. Underwater dive vehicles should be designed to withstand 15 atmospheres of pressure or the pressure that would be encountered at a depth of 500 feet.
The greater the pressure, the more stress there is on the seals which are in place to keep water out of such areas as the buoyancy chambers, the housings surrounding the batteries and the motor. U.S. Pat. No. 4,864,959 recognizes this problem and is directed to detecting leaks of sea water into the battery or motor compartments of underwater dive vehicles. That patent also suggests that water absorbing sheets be stuffed around mechanical parts and the battery and clutch compartments. Another moisture detection system for an underwater dive vehicle is disclosed in U.S. Pat. No. 4,996,938.
Another problem with underwater dive vehicles has to do with the buoyancy of the vehicle. It is highly desirable that at the surface the vehicle have a positive buoyancy so that the unattended vehicle may float on the surface and preferably also support a diver at the surface. However, during the dive., the operator of the vehicle should not be constantly fighting buoyancy.
It is thus an object of the present invention to provide a solution to the water leaks which have heretofore plagued underwater dive vehicles by so constructing the vehicle that the water tight seals are not placed under stress even when the vehicle submerges to depths of several hundred feet.
It is another object of this invention to provide an underwater vehicle the frame of which is open to the water and which thus eliminates any pressure on the frame.
It is a further object of this invention to provide an underwater dive vehicle that has a positive buoyancy at the water surface but which buoyancy may be automatically reduced as the vehicle is taken to greater depths and then becomes neutrally buoyant at depth.
It is an additional object of this invention to provide an underwater vehicle that has an easily adjustable buoyancy which will permit the vehicle selectively to float at the surface of the water, to reduce its buoyancy as the vehicle is descending in the water, to remain at a neutral buoyancy at any selected depth automatically.
The underwater vehicle constructed in accordance with this invention comprises a selectively energizable propulsion unit for forcibly driving said vehicle through the water, and buoyancy means including at least one resilient gas filled buoyancy element and at least one rigid buoyancy element preferably disposed within a buoyancy chamber. There may be one or more buoyancy chambers, each containing one or more buoyancy elements. Each buoyancy chamber is open and thus the buoyancy element is exposed to and is in contact with the surrounding water when said vehicle is in the water, and the volume of gas in said buoyancy element provides sufficient displacement of the water to keep the unattended vehicle afloat at the surface. Since the buoyancy element is exposed and thus in direct contact with the water, when said vehicle is forced downwardly in the water by the propulsion unit the increasing water pressure will act upon and compress the buoyancy element and the gas contained therein reducing the volume of the gas and thus automatically reducing the buoyancy of the buoyancy element until the rigid buoyancy element takes over. The buoyancy element may be a very resilient bladder of rubber or Neoprene which may be conveniently filled with any gas such as air. In the alternative the buoyancy element may be constructed of a foamed, resilient plastic material, such as foamed neoprene, which has discrete isolated pockets or closed cells of entrapped air.
The rigid element may be a rigid foam, for example, an extruded polystyrene foam having a high compressive strength preferably of on the order of between 60 psi and 100 psi. The 60 psi will allow the vehicle to remain neutral to a depth of approximately 141 feet sea water and the 100 psi approximately 235 feet sea water. For greater depths a more rigid foam could be used incased in a rigid tube that is filled with a liquid and sealed or a liquid foam and then sealed. The liquid foam would be something like a two part poor foam like the product seafoam which expands and becomes rigid and would fill all voids in the tube. The vehicle could be coated or filled with a rigid foam and set at neutral buoyancy but would be limited to either fresh or salt water because of different buoyancies of the water.
The advantage of buoyancy chambers is that the buoyancy can be easily adjusted by removing or adding tubes to increase or decrease buoyancy which means that weight or size is no longer a problem nor is going from fresh water to sea water.
Since vehicles have different weights, in order to achieve a neutral buoyancy, you must adjust rigid buoyancy elements first. Once neutral buoyancy is achieved the vehicle will remain neutral to the depth of the rating of the rigid buoyancy you have used. If a positive buoyancy is desired you would then add a resilient gas filled buoyancy element. Therefore one could have any buoyancy affect be it positive, negative or neutral automatically by adding or removing buoyancy. It should also be noted that vehicles at neutral buoyancy are virtually weightless and require less strain on motors to move them through water. For example, submarines, if there was a problem, the vehicle would not sink to deeper depths and implode, but remain neutral and recoverable. Whereas, if an inflatable bladder were added the damaged vehicle could be raised to the surface in an emergency. In one form of the invention the vehicle has a central frame, which is preferably hollow, and the buoyancy means includes a pair of hollow outriggers, open preferably at one or both ends and having arms connected to the central frame of the vehicle. This connection may be fixed or it may be a pivotal connection permitting the outriggers to be pivotally swung between an inwardly folded position overlying the vehicle central frame and an outwardly extended position laterally outward from the frame on opposite sides thereof If the connection is a pivotal connection means is provided for locking the outriggers in their desired position relative to the frame. A buoyancy element, in the form of either a resilient bladder or resilient foamed closed cell plastic is mounted within each of the outriggers and preferably also within the central frame and also a rigid buoyancy element, in the form of a rigid foam or foam filled tube or a rigid gas filled container.
In the preferred embodiment the propulsion unit includes an electric motor having an output shaft on which is mounted a propeller. An electric storage battery supplies the electric current for driving the motor, and a manually operable switch, which may be in the form of a push-button or joystick or turn switch, permits the motor to be selectively energized by the diver-operator. While not preferred, a jet propulsion unit could be employed.
It is preferred that all electrical terminals, such as the terminals for the battery and the motor be encased in a waterproof epoxy resin, so that the sea water will not come into contact with these terminals and cause corrosion. It is preferred that there be unique watertight battery connections and this is a feature of the invention.
The invention also features means for preventing water from entering sealed cavities of the vehicle. This is accomplished by filling those cavities with a non-conductive and noncorrosive liquid, such as transformer oil. Since liquids are substantially non-compressible, seals which are positioned to prevent the entry of sea water into the cavities of the vehicle will be supported by the liquid in the interior of the cavity and will not be distorted by the pressure of the sea water acting through the seal against a compressible and thus non-supporting gas within the cavity. In other words, with liquid in the interior of the cavity, the seal will not be moved inwardly in a manner which would otherwise cause it to distort or stress and permit leakage of sea water into the cavity.